Keyboard instruments and their corresponding software provide so-called play assistants or play assistant modules to enhance the player's comfort. These are software modules that intercept or influence the MIDI (Musical Instrument Digital Interface) digital signals or note events generated by the player on the keyboard's keybed and alter the event stream in such a way that the player can achieve musically complex playing styles while not having to be an expert musician, e.g. harmonizing the played notes or arpeggiation of notes.
A so-called scale mode is known from Apple's GarageBand App for the iPad. The app shows a Marimba-like interface to the user, excluding notes that don't fit a certain scale and root note setting. In particular the black keys are suppressed and not depicted on the screen. The black keys are also called intermediate semitones. In the scale mode, when connecting a standard MIDI keyboard to the iPad, all keys are, however, functioning normally.
Further, many electronic music instruments like MIDI keyboard-controlled synthesizers or samplers provide the player with a so-called control octave, which is a range of one or more keys for switching parameters inside the instrument's software. In most cases, this control octave uses low notes to not interfere with the common note range of the instrument. The player commonly plays the instrument with his right hand. By pressing one or more keys, a digital signal or key event corresponding to the one or more played notes is generated. With the left hand the player plays keys of the control octave, thereby controlling the “sound”, i.e. switching parameters in the instrument software that affect the sound. The control keys are usually non-sounding keys, i.e. no sound is produced by pressing them alone.
Thereby arises the problem that functions of the play assistant module and of the control functionality might interfere and trigger unwanted states of the electronic music instrument.